Collection appliances such as colostomy and ileostomy pouches are vented to permit the escape of intestinal gases and prevent undesirable ballooning of such pouches in use. The vents are commonly provided with porous filter elements at the vent apertures for retaining liquid and/or solid matter within the pouches while selectively allowing the gases to escape. Ideally, such a filter also includes an adsorbent such as activated carbon to extract odors from the gases as they are vented. Although simple in general concept, such gas-venting filters are difficult to construct so that they operate consistently and effectively for the useful life of the appliance, a term ranging from several hours to a week or more depending on the nature of the surgical operation and the particular type of collection appliance involved. Thus, the filter assembly should resist clogging when exposed to solid matter, should be capable of withstanding moisture or even direct contact with liquids, should have sufficient odor-adsorbing capability, and should be constructed so that it cannot be by-passed by gases or, for that matter, by any of the contents of the appliance. In general, prior constructions have been only partially successful in meeting such objectives.
It is therefore an object of this invention to provide an improved gas-venting filter for collection appliances which is far more effective than prior known constructions in preventing the by-passing flow of intestinal gases, which controls or meters the flow of the vented gases so that solids discharged into the bag may pass into the bag's lower portion without encountering obstruction and without at the same time allowing such gases to produce undesirable ballooning of the bag, which resists clogging and the adherence of solid matter discharged into the bag, and which is highly effective in adsorbing odors from the gases as they are vented. A further object is to provide such an improved filter assembly which not only has superior performance characteristics but which also is easier to manufacture and fabricate than gas-venting filter assemblies in current use.
One aspect of this invention lies in the recognition that by-pass problems and other problems associated with gas-venting filters in ostomy appliances might be eliminated or greatly reduced by utilizing thermoplastic fibers in the fabrication of a filter pad, and then heat bonding a gas-pervious liquid barrier layer directly to the pad. Such barrier layer may thereafter be heat sealed directly to a liquid and gas impervious thermoplastic film along a heat seal zone extending about a central opening (or openings) in the film. The film is in turn heat sealed to the inside surface of the collection pouch about the vent aperture thereof with the result that the two concentric seals prevent by-passing of the filter by gases to be vented from the pouch, the non-pervious thermoplastic film performing the additional function of deflecting gases towards and through the adsorbent filter on their way to the vent aperture.
The liquid barrier bonded to the filter pad prevents liquids from entering the pad, and the interior of the pouch to which the filter assembly is secured, without significantly affecting the outflow of gases from the bag. Therefore, an ostomate may wear such a collection device in the shower without fear that water might contact the filter pad and destroy or at least reduce its effectiveness. Similarly, a protective panel which is gas-pervious but liquid-impervious (at least to the extent required for the particular appliance) may be secured by heat sealing to the portion of the thermoplastic film or panel extending beyond the periphery of the pad, thereby enclosing the pad between such panels. The breathable but water-resistant properties of the rear or inside panel protect the porous filter pad from becoming deactivated by liquid within the pouch and the non-adherent character of the polymeric material from which such panel is preferably formed prevents solid and liquid materials within the pouch from blocking the flow of gases through the adsorbent filter and out through the vent opening.
The porosity of the barrier layer and the rear or inside panel of the filter assembly is substantially greater than that of the filter pad itself with the result that the carbon-fiber matrix controls or meters the rate of flow of gas escaping through the vent of a pouch. The filter medium should be of a thickness and composition to provide a value of approximately 10 to 30 seconds when its resistance to the passage of air is measured in accordance with ASTM Test D726-58 (Method A) and, in the final product, the exposed area of the face of the filter pad should fall within the general range of 0.2 to 0.8 square inches.
Other objects, features, and advantages of the assembly will become apparent from the specification and drawings.